The field of the invention is casters and the invention relates more specifically to shopping cart wheels.
For more than twenty years, most high quality shopping cart wheels have utilized bearings which include a pair of all steel races and steel ball bearings. Such bearings are satisfactory for many uses but several trends exist which cause such bearings to be unsatisfactory. First, shopping carts are getting larger and are being used for heavier loads. Large hardware and wholesale outlets tend to lead to shoppers placing far more and far heavier goods in the shopping cart than was the case for the typical grocery shopper.
Another tendency is the use of high-pressure washing systems to clean shopping carts. The carts are periodically placed in the parking lot of the supermarket and high-pressure detergent streams are used to clean the carts but, unfortunately, such streams often wash grease from within the steel wheel bearings. This often results in a very noisy bearing which makes the cart totally unacceptable to the store customers and employees.